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Simple Summary: The role of fatty acid transport protein 1 (FATP1) in decapod crustaceans is still poorly understood. In this study, we cloned the FATP1 cDNA from the mud crab Scylla paramamosain, identified its sequence features and tissue distribution pattern and analyzed its roles in lipid metabolism in vivo. We found that FATP1 is involved in long-chain polyunsaturated fatty acid metabolism and deposition in crustaceans, which provides new information for understanding the function of FATP1 in invertebrates. In mammals, fatty acid transport protein 1 (FATP1) plays important roles in cellular uptake and activation of long-chain fatty acid (LCFA), especially in processes of transportation, oxidation and triacylglycerol synthesis. However, the role of FATP1 in invertebrates, especially decapod crustaceans, is still poorly understood. In this study, the cDNA of a FATP1 gene from a decapod crustacean, mud crab Scylla paramamosain, was cloned and functionally characterized. The FATP1 gene encoded a polypeptide consisting of 643 amino acids that exhibits all the typical features of the FATP family and shares high homology with the other FATP orthologs of crustaceans. The relative mRNA expression levels of FATP1 were observed to be higher in metabolically active tissues such as hepatopancreas, stomach and gill than in other crab parts. Knockdown of the FATP1 mRNA in vivo significantly reduced triacylglycerols and total lipid levels in the hepatopancreas, accompanied by an increase in the expression of genes related to fatty acid transportation, allocation and hydrolysis, including long-chain acyl-CoA synthetase 3/4 (ACSL3/4) and carnitine palmitoyl transferase 1 (CPT1), and a decrease in the expression of genes related to fatty acid synthesis such as acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS) in the hepatopancreas. Furthermore, increased dietary n-3 long-chain polyunsaturated fatty acid (LC-PUFA) levels resulted in the up-regulation of the FATP1 expression in the hepatopancreas, accompanied by an increase in LC-PUFA content, especially eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3), in both polar (PLs) and neutral lipids (NLs) in the hepatopancreas and muscles of crabs. These findings suggested that the FATP1 gene identified in S. paramamosain might play important roles in regulating long-chain fatty acid metabolism and deposition in crustaceans. [ABSTRACT FROM AUTHOR]

As a prerequisite for the success of embryo development, embryonic genome activation (EGA) is an important biological event in which zygotic gene products in the embryo are activated to replace maternal-derived transcripts. Although EGA has been extensively studied in a large number of vertebrates and invertebrates, there is a lack of information regarding this event in crustacean crab. In this study, the timing of EGA was confirmed by examining a transcriptomic dataset of early embryonic development, including mature oocytes and embryos through six early developmental stages, and signaling pathways associated with EGA were identified in the mud crab, S. paramamosain. The comprehensive transcriptomic data identified a total of 53,915 transcripts from these sequencing samples. Notable transcriptomic change was evident at the 1-cell stage, indicated by a 36% transcript number shift and a reduction in transcript fragment length, compared to those present in the mature oocytes. Concurrently, a substantial increase in the expression of newly transcribed transcripts was observed, with gene counts reaching 3485 at the 1-cell stage, indicative of the onset of EGA. GO functional enrichment revealed key biological processes initiated at the 1-cell stage, such as protein complex formation, protein metabolism, and various biosynthetic processes. KEGG analysis identified several critical signaling pathways activated during EGA, including the "cell cycle," "spliceosome," "RNA degradation", and "RNA polymerase", pathways. Furthermore, transcription factor families, including zinc finger, T-box, Nrf1, and Tub were predominantly enriched at the 1-cell stage, suggesting their pivotal roles in regulating embryonic development through the targeting of specific DNA sequences during the EGA process. This groundbreaking study not only addresses a significant knowledge gap regarding the developmental biology of S. paramamosain, especially for the understanding of the mechanism underlying EGA, but also provides scientific data crucial for the research on the individual synchronization of seed breeding within S. paramamosain aquaculture. Additionally, it serves as a reference basis for the study of early embryonic development in other crustacean species. [ABSTRACT FROM AUTHOR]

As rate-limiting enzymes of peroxisomal b-oxidation, acyl-coenzyme A oxidase (ACOXs) play vital roles in maintaining energy homeostasis and regulating reactive oxygen species (ROS) metabolism. However, there are no studies on the functions of ACOXs in crustaceans. In the present study, four full-length cDNA sequences of acoxs, namely the acox-1a (2403 bp), acox-1b (2733 bp), acox-3a (2878 bp) and acox-3b (3445 bp), were successfully isolated from mud crab Scylla paramamosain, which encoded 666, 673, 701 and 658 amino acids, respectively. Sequence analysis showed that the ACOX-1a, ACOX-1b and ACOX-3a possessed conserved structural domains like FAD-binding motif, fatty acyl CoA oxidase domain and peroxisomal targeting signal, while the ACOX-3b lacked peroxisomal targeting signal. Results of phylogenetic tree indicated that the four ACOXs of mud crab grouped gathered with their corresponding orthologues from crustaceans. The acox-1a, acox-3a and acox-3b were highly expressed in hepatopancreas, and the acox-1b was mainly distributed in muscle and hepatopancreas. Compared with feeding groups, the expression levels of acox-1a, acox-3a and acox-3b in hepatopancreas and acox-3a in muscle were markedly up-regulated in fasting groups, suggesting that the acoxs had significant effects in modulating energy balance during fasting. In addition, fasting significantly increased the transcriptional levels of nuclear factor erythroid 2-related factor (nrf2) and its downstream antioxidant genes (catalase (cat), glutathione peroxidase (gpx) and glutathione S-transferase (gst)) to improve antioxidant capacity for removing excessive ROS produced by ACOX-mediated peroxisomal b-oxidation. These results would be conducive to providing new insights into evolutionary characteristics and functions of acoxs in crustaceans. [ABSTRACT FROM AUTHOR]

In this study, we added LDN-193189 2HCL to inhibit the BMP signaling pathway in Scylla paramamosain and then explored the function of this pathway in molting through the changes in the growth performance and molt-related gene expression. The study findings indicated that the expression of ACVR1, BMPRIB, and Smad1 in Scylla paramamosain was suppressed when the LDN-193189 2HCL concentration in the culture water was 2 µm/L. Subsequently, following a 30-day experiment, there was a significant reduction in the molting frequency, growth rate, and body size of the S. paramamosain larvae. An analysis of the BMP pathway gene expression during the molting phase revealed that the BMP2, BMPR2, and Smad1 genes displayed cyclic expression patterns, while ACVR1, BMP7, and BMPRIB maintained consistent expression levels throughout the molting cycle. Additionally, the expression levels of BMP2, BMPR2, and Smad1 in the inhibition group were significantly lower compared to those in the control group. Furthermore, the inhibition of the BMP pathway led to an increase in the expression of MIH during the intermolt period and a decrease in the expression of EcR during the premolt period. These findings demonstrate that the BMP signaling pathway affects the molting of Scylla paramamosain juvenile crabs by influencing the expression of the critical genes MIH and ECR during molting, offering valuable data for functional research on the BMP signaling pathway in crustaceans. [ABSTRACT FROM AUTHOR]

The farming of Scylla paramamosain with specific flavors has a higher commercial value, and the flavors are related to the integrated farming environment and non-volatile flavor substances, while the survival environment is one of the important ways to source gut microorganisms in the organism. In this study, the levels of dominant taxa in the gut flora of S. paramamosain from Mong Cai, Vietnam (VN), Taishan City, Guangdong Province (TS) of China, and Ninghai County, Ningbo City (NB) Zhejiang Province of China converged with those of S. paramamosain from Sanmen County, Ningbo City (CK1, CK2, and CK3) at 28 d of domestication. The top 15 genera with the highest abundance of VN, TS, and NB gut flora were the same as CK1, CK2, and CK3, but with different percentages, and gradually converged to CK1, CK2, and CK3, respectively, at 28 d of domestication. Correlation between intestinal flora and non-volatile flavor substances in the hepatopancreas at the percentage level of relative abundance of bacterial genera found that above 28 d of domestication, Muribaculaceae, Psychrilyobacter, Clostridia_vadinBB60_group, Halarcobacter Carboxylicivirga, Sediminispirochaeta may be the most important genera affecting flavor amino acids of VN. Sediminispirochaeta, Carboxylicivirga, Halarcobacter, Photobacterium, ZOR0006, Psychrilyobacter, and Pseudomonas may be the most important genera affecting flavor amino acids of NB. Sediminispirochaeta, Carboxylicivirga, Halarcobacter, Photobacterium, ZOR0006, Vibrio, and Sphingomonas may be the most important genera affecting flavor amino acids of TS. These results show that the intestinal flora structure of crabs from different areas were domesticated in the same area for at least 28 d before they converged to that of the domesticated crab, and the most important genera affecting the flavor amino acids of TS, VN, and NB were also identified. The results of this study provide a reference and basis for the technique of directional cultivation of the flavor quality of the crab. [ABSTRACT FROM AUTHOR]

Scylla paramamosain is an euryhaline species that is extensively distributed in coastal regions along the Indian and Pacific Oceans. Recently, S. paramamosain are considered as species that can be cultured in low-salinity areas to improve the local economy. However, the long-term effects and mechanisms of low salinity on its physiology remain unclear. In this study, S. paramamosain were reared in low-salinity (5 ppt) and normal sea-water environment (25 ppt) for 30 days. We compared haemolymph osmolality, gill structure, and transcriptome changes between the two groups. Results indicated that S. paramamosain subjected to a low-salinity environment showed gill damage such as broken lamellar and reduced haemocytes, some adaptive responses as increased mitochondria in chloride cells were also observed. Even with decreased water ion concentration in lower salinity, the concentrations of Na+, K+, and Cl- in the haemolymph of crab were remained higher than the surrounding water. Transcriptomic analysis revealed 2086 differentially expressed genes, including significant alterations in genes like hexosaminidase and neprilysin. Enriched pathways linked to ion transport were identified, highlighting the main adaptive mechanisms in long-term hypotonic environments. Our findings elucidated the effects and mechanism of long-term low salinity on gill structure and osmoregulation in S. paramamosain, providing theoretical basis for the development of low salinity aquaculture technology of this species.

To compare the allergenicity of native arginine kinase (nAK) and recombinant AK (rAK) from Scylla paramamosain and to identify the predominant allergenic domain of AK, AK was divided into 4 fragments: AK-E1 (amino acid (AA) 1–92), AK-E2 (AA 87–187), AK-E3 (AA 172–265), and AK-E4 (AA 276–357) based on the distribution of epitopes and the spatial structure of the AK molecule. The four recombinant fragments were expressed in the prokaryotic system Escherichia coli, and then nAK, rAK, and the recombinant fragments were purified. The allergenicity of recombinant proteins were evaluated using BALB/c mice. The results showed that the levels of specific antibodies in the serum and the secretion of Th2 type cytokines by the splenocytes of mice sensitized with rAK significantly increased, but the immunogenicity of rAK was weaker than that of nAK. Among the 4 fragments of AK, AK-E2 had the strongest immunogenicity. Meanwhile, rAK could stimulate RBL-2H3 cells to release β-hexokinase, but it was less effective than nAK. Among the 4 expressed fragments, AK-E2 and AK-E4 had a stronger stimulating effect on effector cells. In conclusion, the rAK expressed in the prokaryotic system showed weaker immunogenicity than nAK, and among the 4 fragments of AK, AA 87–187 has the strongest immunogenicity while AA 276–357 has the strongest immunoreactivity.

A 2 × 3 two-factor experiment was designed to assess the effects of dietary cholesterol (CHO) and phospholipids (PLs) on growth and lipid metabolism in early juvenile mud crabs (0.01 g crab−1). The experimental diets were designed with two CHO levels: 0.40 % (LCH) and 0.80 % (HCH), and three PLs levels: 1.80 % (LPL), 2.50 % (MPL), and 3.20 % (HPL). The 58-day aquaculture trial demonstrated that the LCH-HPL group achieved the best growth performance in mud crabs, characterized by the highest final body weight, weight gain, and specific growth rate. Regarding whole-body composition, dietary PLs increased total cholesterol (T-CHO), PLs, triglyceride (TG), and crude lipid content in the LCH groups. Mud crabs in the HCH groups had a higher proportion of saturated fatty acids, a lower proportion of monounsaturated fatty acids, and increased gene expression of sterol regulatory element binding protein 1c (srebp-1c) and fatty acid synthase (fas) compared to those in the LCH groups. As the dietary PLs increased, mud crabs in the LCH groups exhibited up-regulation in the expression of genes, including srebp-1c, fas, elongation of very long-chain fatty acid protein 4 (elovl4), elovl6, and Δ9-fatty acid desaturase (Δ9-fad). In the HCH groups, elevated dietary PLs resulted in the down-regulation of fatty acid binding protein (fabp) gene expression. In addition, high levels of dietary CHO and PLs (HCH-HPL) inhibited the catalase activity of mud crabs, resulting in a significant increase in the malondialdehyde content. Correlation analysis revealed that dietary CHO was positively correlated with the expression of long-chain polyunsaturated fatty acids synthesizing genes, and dietary PLs were positively correlated with the whole-body lipid content of mud crabs. Additionally, a positive correlation was found between the growth performance and whole-body content of crude protein, crude lipid, and antioxidant capacity in mud crabs.

The mud crab (Scylla paramamosain) is an important species for seawater aquaculture, the utilization of saline-alkali water provides potential for the further development of the mud crab industry, but the adaptation mechanism of the antennal gland to chloride type low-salt saline-alkali water has not been fully studied. In this study, we evaluated the osmoregulatory enzyme activity (n=3) and metabolic changes (n = 5) of the antennal gland in S. paramamosain after a sudden drop in salinity from 23 ‰ of seawater to 2 ‰ of chloride type low-salt saline-alkali water. After the decrease in salinity, the activity of osmoregulatory enzymes in the antennal gland, including Na+/K+-ATPase, NKCC, carbonic anhydrase (CA), and V-ATPase showed a trend of first increasing and then decreasing. Through LC-MS technology, we identified 308 differential metabolites. In addition, KEGG enrichment analysis identified eight significant metabolic pathways (P

Oviposition is induced upon mating in most insects. Spawning is a physiological process that is fundamental for the reproduction of Scylla paramamosain. However, the molecular mechanisms underlying the spawning process in this species are poorly understood. Herein, comprehensive ovary transcriptomic analysis was conducted at the germinal vesicle breakdown stage (GVBD), spawning stage, 0.5 h post‐spawning stage, and 24 h post‐spawning stage of S. paramamosain for gene discovery. A total of 67,230 unigenes were generated, and 27,975 (41.61%) unigenes were annotated. Meanwhile, the differentially expressed genes (DEGs) between the different groups were identified, and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis was subsequently conducted. These results suggested that octopamine (OA) and tyramine (TA) could induce oviposition, while dopamine (DA) and serotonin (5‐hydroxytryptamine [5‐HT]) inhibit oviposition. The 20‐hydroxyecdysone (20E) and methyl farnesoate (MF) signal pathways might be positively associated with oviposition. Furthermore, numerous transcripts that encode neuropeptides and their G‐protein‐coupled receptors (GPCRs), such as CNMamide, RYamide, ecdysis‐triggering hormone (ETH), GPA2/GPB5 receptor, and Moody receptor, appear to be differentially expressed during the spawning process. Eleven unigenes were selected for qRT‐PCR and the pattern was found to be consistent with the transcriptome expression pattern. Our work is the first spawning‐related investigation of S. paramamosain focusing on the ovary at the whole transcriptome level. These findings assist in improving our understanding of spawning regulation in S. paramamosain and provide information for oviposition studies in other crustaceans. [ABSTRACT FROM AUTHOR]

As rate-limiting enzymes of b-oxidation of fatty acids in mitochondria, the carnitine palmitoyltransferase (CPT) played an important role in regulating energy homeostasis of aquatic animals. However, there was very little research on b-oxidation of fatty acids in crustaceans. In the present study, the full-length cDNA sequences of cpt-1a, cpt-1b and cpt-2 were isolated from the hepatopancreas of Scylla paramamosain, and contained 4206, 5303 and 3486 bp respectively. Sequence analysis showed that the CPT-1A, CPT-1B and CPT-2 encoded proteins with 777, 775 and 672 amino acids respectively, and only the CPT-1A possessed a transmembrane region. In addition, both the CPT-1B and CPT-2 contained conservative functional domains like N-terminal domain and acyltransferases choActase 2, while the CPT-1A lacked. The results of phylogenetic tree indicated that the CPT-1A, CPT-1B and CPT-2 of S. paramamosain gathered together with their corresponding orthologues from crustaceans. The tissue distribution exhibited that the cpt-1a was highly expressed in hepatopancreas, followed by muscle, eyestalk and cranial ganglia, and the muscle, eyestalk and heart were main expressed tissues of cpt-1b. Furthermore, the high expression levels of cpt-2 were mainly detected in hepatopancreas, muscle and heart. The transcriptional levels of cpt-1a, cpt-1b and cpt-2 were significantly up-regulated under chronic low salinity stress. Besides, at the acute low salinity stress condition, the expression levels of cpt-1a, cpt-1b and cpt-2 in hepatopancreas were dramatically increased in 14°C and 4°C salinity groups at the 6h and 48h, while the transcriptional levels of cpt-1a, cpt-1b and cpt-2 in muscle were signally up-regulated in 14°C and 4°C salinity groups at the 12h and 24h, showing an alternate response pattern. Similarly, the present study found that fasting could markedly increase the expression levels of cpt-1a, cpt-1b and cpt-2 in hepatopancreas and muscle, especially cpt-1a in hepatopancreas as well as cpt-1a and cpt-1b in muscle. The results above indicated that the cpt-1a, cpt-1b and cpt-2 played a crucial part in providing energy for coping with fasting and salinity stress. These results would contribute to enhancing the knowledge of cpt phylogenetic evolution and their roles in energy metabolism of crustaceans. [ABSTRACT FROM AUTHOR]

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Light is an essential ecological factor that has been demonstrated to affect aquatic animals' behavior, growth performance, and energy metabolism. Our previous study found that the full-spectrum light and cyan light could promote growth performance and molting frequency of Scylla paramamosain while it was suppressed by violet light. Hence, the purpose of this study is to investigate the underlying molecular mechanism that influences light spectral composition on the growth performance and molting of S. paramamosain. RNA-seq analysis and qPCR were employed to assess the differentially expressed genes (DEGs) of eyestalks from S. paramamosain reared under full-spectrum light (FL), violet light (VL), and cyan light (CL) conditions after 8 weeks trial. The results showed that there are 5024 DEGs in FL vs. VL, 3398 DEGs in FL vs. CL, and 3559 DEGs in VL vs. CL observed. GO analysis showed that the DEGs enriched in the molecular function category involved in chitin binding, structural molecular activity, and structural constituent of cuticle. In addition, the DEGs in FL vs. VL were mainly enriched in the ribosome, amino sugar and nucleotide sugar metabolism, lysosome, apoptosis, and antigen processing and presentation pathways by KEGG pathway analysis. Similarly, ribosome, lysosome, and antigen processing and presentation pathways were major terms that enriched in FL vs. CL group. However, only the ribosome pathway was significantly enriched in up-regulated DEGs in VL vs. CL group. Furthermore, five genes were randomly selected from DEGs for qPCR analysis to validate the RNA-seq data, and the result showed that there was high consistency between the RNA-seq and qPCR. Taken together, violet light exposure may affect the growth performance of S. paramamosain by reducing the ability of immunity and protein biosynthesis, and chitin metabolism. [ABSTRACT FROM AUTHOR]

Salinity affects the growth and development of crustaceans by affecting their physiological functions such as respiration, metabolism, osmotic regulation and immune defense. Gill is the most important organ of osmotic regulation. The adaptation of Scylla paramamosain to low salt is a process of oxygen consumption and energy consumption, and the mitochondria in the cells are considered to be the synthesis site of energy. Therefore, in this study, GC-MS technology was used to conduct non-targeted metabolomics studies on the posterior gill mitochondria of S. paramamosain under acute hyposaline stress, revealing the key role of mitochondria in gill response to acute low salinity stress. We identified 196 metabolites, 21 of which were differentially expressed. Differential metabolite KEGG enrichment analysis identified 16 metabolic pathways. The results of this study suggest that mitochondria may maintain osmotic homeostasis by increasing the utilization of monosaccharides, and decreasing the synthesis of amino acids in crabs under acute low salt stress when they are in a state of oxygen and energy depletion. In addition, carbohydrates and organic acid metabolites may also play an important role. For the first time, we analyzed the metabolic mechanism of posterior gill mitochondria in response to acute low salt, aiming to provide effective technical support and theoretical reference for the cultivation of S. paramamosain.

Scylla paramamosain is an important mariculture animal. In the present study, we examined the physiological and biochemical characteristics of juvenile S. paramamosain under hypoosmotic stress and further verified the function of ABCC1, a key transport protein in gill tissue. The results showed that Na+/K+-ATPase, Ca2+-ATPase, and Na+/K+/2Cl- cotransporter in gill tissues increased first and then decreased. In addition, SOD and CAT activities also began to gradually increase, protecting gill tissues from oxidative damage. The hemolymph osmolarity decreased rapidly from 792 mOsm/kg to 560 mOsm/kg within 6 h, and then rose to 626.25 mOsm/kg at 48 h, and then remained stable. At the same time, Na+, Cl-, K+, and Ca2+ concentrations were decreased to varying degrees. There were significant changes in free amino acids such as aspartic acid, glutamic acid, and asparagine in hemolymph in response to acute salt depletion. By injection of ABCC1 inhibitor/activator, it was found that while ABCC1 transporter activity in the MK-571 group showed a decreasing trend at 9 h, Na+/K+ -ATPase activity began to increase and reached a peak at 48 h. Compared with the control group, the levels of aspartic acid, glutamic acid, asparagine, glycine, arginine, alanine, lysine, and proline in the MK-571 group showed significant differences at 6 h; Significant differences in glutamate, asparagine, arginine, alanine, lysine, and proline appeared at 12 h in the Thiethylperazine group. These results suggested that the dynamic changes of gill ion transport enzymes, antioxidant enzymes, inorganic ions, and free amino acids in hemolymph occurred in S. paramamosain under hypoosmotic stress, and the ABCC1 transporter played an important role in this regulatory process.

A six-week feeding trial was conducted to investigate the effects of dietary starch levels on growth performance, glucose and lipid metabolism and insulin signaling pathway of juvenile Scylla paramamosain. Three isonitrogenous (41.51% ± 0.31%) and isolipidic (8.68% ± 0.53%) experimental diets were formulated to contain 10%, 20% and 30% starch levels, respectively. A total 96 crabs were divided into 3 treatment groups. There were 4 replicates per treatment group and 8 crabs per replicate (initial weight 5.12 ± 0.05 g). The crabs fed the diet with 20% starch showed the best growth performance, with higher weight gain rate (WGR), specific growth rate (SGR), protein efficiency ratio (PER), and feed efficiency (FE) compared to the other diets. Increasing starch levels in the diet resulted in higher levels of glycogen and lipid in the muscles and hepatopancreas. The levels of glucose (GLU), triglyceride (TG), and free fatty acid (FFA) displayed a significant increase in both hemolymph and hepatopancreas with the escalating dietary starch concentrations. In contrast, as the dietary starch levels increased, the concentrations of crustacean hyperglycemic hormone (CHH) and insulin-like peptides (ILPs) in hemolymph and hepatopancreas demonstrated a notable decline. The glycolysis and pentose phosphorylation pathways were significantly promoted, while the gluconeogenic pathway was significantly inhibited, with dietary starch levels increasing from 10% to 30%. Additionally, increasing dietary starch levels led to a significant down-regulation of genes related to the lipid synthesis, lipolysis and insulin signaling pathway. Histological results showed that hepatopancreas fat accumulation increased with the increase of dietary starch level. Overall, the findings of this study suggest that adding 20% starch to the diet can promote growth and improve nutrient utilization. In addition, the level of dietary starch had significant effects on the glucose and lipid metabolism and insulin signaling pathway of mud crabs, thus affecting the deposition of lipid reserves in hepatopancreas.

In mammals, fatty acid transport protein 1 (FATP1) plays important roles in cellular uptake and activation of long-chain fatty acid (LCFA), especially in processes of transportation, oxidation and triacylglycerol synthesis. However, the role of FATP1 in invertebrates, especially decapod crustaceans, is still poorly understood. In this study, the cDNA of a FATP1 gene from a decapod crustacean, mud crab Scylla paramamosain, was cloned and functionally characterized. The FATP1 gene encoded a polypeptide consisting of 643 amino acids that exhibits all the typical features of the FATP family and shares high homology with the other FATP orthologs of crustaceans. The relative mRNA expression levels of FATP1 were observed to be higher in metabolically active tissues such as hepatopancreas, stomach and gill than in other crab parts. Knockdown of the FATP1 mRNA in vivo significantly reduced triacylglycerols and total lipid levels in the hepatopancreas, accompanied by an increase in the expression of genes related to fatty acid transportation, allocation and hydrolysis, including long-chain acyl-CoA synthetase 3/4 (ACSL3/4) and carnitine palmitoyl transferase 1 (CPT1), and a decrease in the expression of genes related to fatty acid synthesis such as acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS) in the hepatopancreas. Furthermore, increased dietary n-3 long-chain polyunsaturated fatty acid (LC-PUFA) levels resulted in the up-regulation of the FATP1 expression in the hepatopancreas, accompanied by an increase in LC-PUFA content, especially eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3), in both polar (PLs) and neutral lipids (NLs) in the hepatopancreas and muscles of crabs. These findings suggested that the FATP1 gene identified in S. paramamosain might play important roles in regulating long-chain fatty acid metabolism and deposition in crustaceans.

Variability in food availability leads to condition-dependent investments in reproduction. This study is aimed at understanding the metabolic response and regulatory mechanism of female Scylla paramamosain in response to starvation in a temporal- and tissue-specific manner. The mud crabs were starved for 7 (control), 14, 28, and 40 days for histological and biochemical analysis in the hepatopancreas, ovary, and serum, as well as for RNA sequencing on the hepatopancreas and ovary. We further highlighted candidate gene modules highly linked to physiological traits. Collectively, our observations suggested that starvation triggered endogenous ovarian maturation at the expense of hepatopancreas mass, with both metabolic adjustments to optimize energy and fatty acid supply from hepatopancreas to ovary in the early phase, followed by the activation of autophagy-related pathways in both organs over prolonged starvation. These specific adaptive responses might be considered efficient strategies to stimulate ovarian maturation of Scylla paramamosain under fasting stress, which improves the nutritional value of female mud crabs and other economically important crustaceans. [ABSTRACT FROM AUTHOR]

The mud crab Scylla paramamosain is a valuable commercial mariculture crab worldwide. During the ebb tide or when transported to market, crabs suffer underlying air exposure stress. Gills tissue is the first tissue to cope with this stress. In this study, the transcriptome of S. paramamosain gills from the control group (CG) and experimental group (EG) were sequenced, assembled, and compared. A total of 7,425,620,293 bp and 6,741,616,977 bp clean data were found in EG and CG, respectively. A total of 38,507 unigenes (42.78%) were annotated successfully. 13,626 differentially expressed genes (DEGs) were up-regulated, and 6,502 DEGs were down-regulated. The DEGs related to immunity, apoptosis, metabolism, and ion exchange were detected. DEGs were enriched significantly into the KEGG pathways related to metabolism and immunity. These results proved that more material and energy were required, and immune defense was enhanced when the crab was under air exposure stress. The present study provides the first-gill transcriptomic analysis challenged with air exposure stress in S. paramamosain under air exposure stress, which will be useful to clarify the molecular mechanisms of air exposure adaptation. [ABSTRACT FROM AUTHOR]

Mud crabs (Scylla genus) are luxury foods in high demand internationally. The efficient techniques for mud crab hatcheries are vital for providing breeds for their aquaculture, which is rapidly growing in many countries. This study aims to investigate the effects of different feeds and stocking densities on mud crabs' growth and survival rates (Scylla paramamosain) in the stage from megalopa to crablet-1 stage. Two separate experiments were conducted indoors in the 60-liter round plastic tanks (containing 50 liters of water at a 28° salinity). Experiment 1 investigated four feeds: frozen Artemia biomass, pureed shrimp meat, Lansy pellet feed (48% protein), and NRD pellet feed (55% protein). Megalopae (mean weight of 5.8 mg) were stocked at a density of 10/L. In experiment 2, the megalopae (mean weight of 5.4 mg) were stocked at densities of 20, 30, and 40/L and were fed the Lansy pellet feed, which was the best one selected from experiment 1. High survival rates were obtained at all four feeds (82.2-87.5%) and three stocking densities (88.4-90.1%). The growth performances in Lansy feed and frozen Artemia biomass were better than those in pureed shrimp meat and NRD pellet feed, which was seen through higher indicators of daily weight gain (DWG) and specific growth rate in weight (SGRw) (p < 0.05). Despite the survival rate showing no significant difference among the feeds, their highest value (87.5%) was observed in the Lansy pellet feed. On the other hand, the growth performances showed a significant decrease at stocking densities = 30/L, as complemented by a significant decrease in DWG and SGRw at these stocking densities (p < 0.05). Both survival rate and metamorphosis durations did not show significant differences among the feeds or stocking densities (p > 0.05). The investigated feeds and stocking densities suit the nursing mud crab (S. paramamosain) megalopa. In contrast, the Lansy pellet feeds had a stocking density of 20/L, resulting in the highest nursing efficiency. [ABSTRACT FROM AUTHOR]

To solve the industrial bottlenecks of the traditional pond aquaculture of the Scylla paramamosain, such as mutual killing,severe losses caused by natural disasters,and the cumbersome operation of the existing factory circulating aquaculture system of “Crab Apartment”,the Scylla paramamosain was cultured in the " Dragon Boat" type factory circulating aquaculture system and the factory circulating aquaculture system of " Crab Apartment" designed in this experiment. The breeding cycle was 30 d. The study aimed compare the survival rate,aquaculture water environment,growth performance and nutritional quality. The results showed as follows:The survival rate of the Scylla paramamosain in the dragon-boat type factory circulating aquaculture system was ( 98. 66 ± 0. 58) %, which was significantly higher than that in the crab apartment factory circulating aquaculture system ( P < 0. 05). In the " Dragon Boat" type industrial recirculating aquaculture system,the ammonia nitrogen content was 0. 062 5-0. 067 1 mg / L,the nitrite nitrogen content was 0. 021 3- 0. 025 3 mg / L,and the active phosphate content was 0. 031 5-0. 034 6 mg / L,all of which were lower than that in the " Crab Apartment" industrial recirculating aquaculture system. The body weight specific growth rate of the " Dragon Boat" type factory recirculating aquaculture system was ( 3. 43 ± 0. 50) % / d, the molting interval time was (20. 4±0. 25) d,and the growth performance was significantly higher than that of the " crab flat" factory recirculating aquaculture system (P<0. 05). The essential amino acid index (E) in muscle of the Scylla paramamosain cultured in the " Dragon Boat" type industrial recirculating aquaculture system was 67. 35,which was higher than that in the " Crab House" industrial recirculating aquaculture system; The fatty acid composition and quality safety of muscle were better than that of " Crab Apartment" industrial circulating aquaculture system. The results showed that the adoption of the " Dragon Boat " type industrial recycle aquaculture system could reduce water pollution,improve the survival rate and growth rate of the crab,improve muscle nutrition and reduce the content of heavy metals in the muscle,which could be used as a new model for the industrial culture of the crab. [ABSTRACT FROM AUTHOR]

Anesthesia serves as an effective method to mitigate the stress response in aquatic animals during aquaculture and product transportation. In this study, we assessed the anesthetic efficacy of clove oil, tricaine methane-sulfonate (MS-222), ethanol, and magnesium chloride by anesthesia duration, recovery time, 24-hour survival rate, and the behavior of mud crabs (Scylla paramamosain). Additionally, the optimal anesthetic concentration for varying body weights of mud crabs was also investigated. The results revealed that clove oil emerged as the optimal anesthetic for mud crabs, with a 24-hour survival rate surpassing those observed in MS-222 and magnesium chloride treatments. Ethanol caused amputation and hyperactivity in mud crabs. Regression analyses between the optimal anesthetic concentration of clove oil and the weight categories of 0.03–27.50 g and 27.50–399.73 g for mud crabs yielded the following equations: y = 0.0036 x3 − 0.1629 x2 + 1.7314 x + 4.085 (R2 = 0.7115) and y = 0.0437 x + 2.9461 (R2 = 0.9549). Clove oil exhibited no significant impact on serum cortisol, glucose, lactate content, aspartate aminotransferase (AST), alanine aminotransferase (ALT) activities, or superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), and malondialdehyde (MDA) levels in mud crabs across different treatment groups. Anesthesia induced by clove oil in mud crabs resulted in an increase in inhibitory neurotransmitters such as glycine. However, the recovery from anesthesia was associated with elevated levels of the excitatory neurotransmitters L-aspartic acid and glutamate. In conclusion, clove oil proves to be a safe and optimal anesthetic agent for mud crabs, exerting no physiological stress on the species. [ABSTRACT FROM AUTHOR]

Lipid accumulation in ovaries is essential for reproductive success in decapods. Understanding of the mechanism of ovarian lipid accumulation is still in its infancy. In this study, we investigated lipid compositions of ovaries and hepatopancreas throughout vitellogenesis and hemolymph in the late-vitellogenic stage in the mud crab Scylla paramamosain. Total lipid content in ovaries consecutively increased from the early to late stage, and the main accumulated lipids were phosphatidylcholine (PC), alkenylglycerophosphoethanolamine (alkenyl-PE), triacylglycerol (TG), cholesteryl ester, and cholesterol. The lipid composition of hemolymph indicated that PC, alkenyl-PE, diacylglycerol (DG), ether DG, monoacylglycerol, and cholesterol were the main lipids transferred to ovaries from hepatopancreas. In hepatopancreas, the total lipid content appeared to increase during vitellogenesis and the late stage was significantly different from early and mid-stages. TG was the predominant lipid class that slightly decreased from the early to mid-stage, but dramatically increased in the late stage. In contrast, PC and alkenyl-PE significantly increased from the early to mid-stage and remained constantly in relatively low proportion until the late stage. These findings suggested PC and alkenyl-PE in the hepatopancreas likely play critical roles in regulating lipid transfer. Esterified fatty acids in ovaries and hepatopancreas were mainly C16:0, C18:0, 16:1, C18:1, C18:2, C20:4, C20:5, and C22:6, of which highly unsaturated fatty acids (HUFA) primarily occurred in alkenyl-PE and phosphatidylserine (PS) but not PC. In hemolymph, PC was abundant in HUFA besides of saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA), while PS was predominantly composed of SFA and MUFA, implying a transformation of HUFA between phospholipids prior to transfer. These findings highlight the importance of phospholipid metabolism in the hepatopancreas to ovarian lipid accumulation. Our study provides novel insights into the mechanism of ovarian lipid accumulation in decapods.

The feeding rhythm is one of the key factors determining the success of artificial breeding of S. paramamosain. To understand the feeding rhythm of the different zoea larva developmental stages of S. paramamosain, the feeding rate, digestive enzyme activity, and expression of metabolism-related genes were investigated in the present study. The results showed that the S. paramamosain feeding rate has strong diurnal feeding rhythm, being significantly higher at 10:00–14:00 from stages ZI to ZIV. While the feeding rate peaked at 14:00 on Days 10 and 11, the peak shifted to 18:00 on Day 12. The activity of digestive enzymes amylase, pepsin and lipase decreased at night but increased in the daytime, showing a single-phase rhythm similar to that of the feeding rate, suggesting that the digestive enzyme activity was closely associated with the feeding rate during the larval development. Compared to pepsin and lipase, the activity of amylase was the most consistent with feeding rate. In particular, amylase activity peaked at 18:00 on Day 12. Due to its synchronicity with feeding activity, the activity of amylase could provide a potential reference for determining the best feeding time during zoea stages in S. paramamosain breeding. Moreover, the relative mRNA expression of metabolism-related genes SpCHH and SpFAS at most tested points was lower from 10:00 to 14:00, but higher at 18:00 to 6:00 of the next day. On the other hand, the expression patterns of SpHSL and SpTryp were converse to those of SpCHH and SpFAS. Our findings revealed that the S. paramamosain zoea has an obvious feeding rhythm, and the most suitable feeding time was 10:00–18:00 depending on different stages. The feeding rhythm is a critical aspect in aquaculture, influencing a series of physiological functions in aquatic animals. This study provides insights into the feeding rhythm during the zoea development of S. paramamosain, making a significant contribution to optimizing feeding strategy, improving aquafeed utilization, and reducing the impact of residual feed on water environment.

The mud crab Scylla paramamosain is a key species in China due to its high nutritional value and great economic worth and has grown in popularity. Myo-inositol can modulate versatile physiological functions in aquatic animals. In the present study, S. paramamosain megalopa were given graded concentrations of myo-inositol (0, 1, 2, 4, and 8 ppm) by water immersion to explore how their metamorphosis would be affected. The results showed that supplementing with myo-inositol remarkably increased transformation and survival rate from megalopa to crablet by at least 1.16 and 1.26 times, respectively. To decipher the molecular mechanism of how myo-inositol increases metamorphosis and survival rate, we further performed transcriptome-based gene expression profiling of both megalopa and crablet treated with myo-inositol. The integrative transcriptome analyses predicted that the differentially expressed genes (DEGs) were significantly enriched in chitinase activity, structural constituent of cuticle, and chitin binding, which are associated with the decomposition and reconstruction of cuticle. qPCR results confirmed that myo-inositol mediated gene expression levels of the above cuticle-related pathways. Considering the importance of the cuticle in exoskeleton formation and molting, it can be concluded that myo-inositol-induced changes in the cuticle decomposition and reconstruction might have accelerated the transformation from megalopa to crablet of S. paramamosain. Besides, numerous DEGs were significantly enriched in protein digestion and absorption, amino sugar and nucleotide sugar metabolism. It implies that myo-inositol may improve survival by regulating energy or nutrient absorption. Additionally, the accelerated metamorphosis by myo-inositol may improve survival from megalopa to crablet of S. paramamosain. Overall, this study will provide the first insights into the underlying molecular mechanisms by which myo-inositol increases metamorphosis and survival.

In this study, we added LDN-193189 2HCL to inhibit the BMP signaling pathway in Scylla paramamosain and then explored the function of this pathway in molting through the changes in the growth performance and molt-related gene expression. The study findings indicated that the expression of ACVR1, BMPRIB, and Smad1 in Scylla paramamosain was suppressed when the LDN-193189 2HCL concentration in the culture water was 2 µm/L. Subsequently, following a 30-day experiment, there was a significant reduction in the molting frequency, growth rate, and body size of the S. paramamosain larvae. An analysis of the BMP pathway gene expression during the molting phase revealed that the BMP2, BMPR2, and Smad1 genes displayed cyclic expression patterns, while ACVR1, BMP7, and BMPRIB maintained consistent expression levels throughout the molting cycle. Additionally, the expression levels of BMP2, BMPR2, and Smad1 in the inhibition group were significantly lower compared to those in the control group. Furthermore, the inhibition of the BMP pathway led to an increase in the expression of MIH during the intermolt period and a decrease in the expression of EcR during the premolt period. These findings demonstrate that the BMP signaling pathway affects the molting of Scylla paramamosain juvenile crabs by influencing the expression of the critical genes MIH and ECR during molting, offering valuable data for functional research on the BMP signaling pathway in crustaceans.

Apoptosis Inhibitor 5 (API5) is a widely concerned nuclear protein with diverse functions in organisms, so far, study of API5 is still quite limited in lower animals, and its role in viral immune response has not been addressed. Here, we explored the function of API5 in mud crab (Scylla paramamosain) during White Spot Syndrome Virus (WSSV) infection. The interacting protein Hsp20 of API5 was screened by pull-down assay, and API5 and hsp20 were knocked down by RNAi interference. The results showed that API5 was upregulated along with virus infection, silencing of API5 led to increased WSSV copy numbers and apoptotic rate of hemocytes, highlighting its significance in the immune response. Moreover, we discovered a novel interaction between API5 and Heat Shock Protein 20 (Hsp20), and then revealed that Hsp20 could promote cell apoptosis of hemocytes and reduce viral copy numbers by suppressing API5. The current study therefore improves the knowledge of API5-Hsp20 axis and provides novel insights into intricate mechanisms governing the antiviral response in marine crustaceans.

Introduction: The mud crab, Scylla paramamosain, holds great commercial significance as a marine crustacean widely cultivated in the Indo-Pacific region. Understanding the core gut microbiota of aquatic animals is crucial for their overall health and growth, yet the core gut microbiota of mud crab remains poorly characterized. Methods: In this study, we gathered gut samples from mud crabs across five locations within Sanmen Bay, China. Through the utilization of high-throughput sequencing, we delved into the composition of the gut microbial community and identified the core gut microbiome of mud crab. Results: Our results demonstrate that the gut microbial diversity of mud crab did not exhibit significant variation among the five sampling sites, although there were some differences in community richness. At the phylum level, we identified 35 representative phyla, with Firmicutes, Proteobacteria, Bacteroidota, and Campilobacterota as the dominant phyla. Among the 815 representative genera, we discovered 19 core genera, which accounted for 65.45% of the total sequences. These core genera were distributed across 6 phyla, and among them, Photobacterium exhibited the highest average relative abundance. Discussion: Photobacterium has probiotic activity and may play a crucial role in enhancing the immune response of the host and maintaining the diversity of the gut microbiota. Moreover, we observed a positive correlation between the relative abundance of core genera and the stability of the gut microbial community. Furthermore, our findings revealed distinct differences in gut microbial composition and specific taxa between the sexes of mud crab. These differences subsequently influenced the functionality of the gut microbial community. Overall, our investigation sheds light on the core gut microbiota of mud crab, emphasizing the importance of core gut microbial communities in maintaining the health and growth of these commercially significant marine crustaceans. [ABSTRACT FROM AUTHOR]

To investigate the embryonic development of the mud crab Scylla paramamosain, we analyzed three critical parameters: egg color of, embryo morphology (through conventional and laser scanning confocal microscopy), and the distribution of cell divisions. During embryonic development, the egg color exhibited a progressive transition, shifting from orange to reddish-orange, then to brown, before ultimately darkening to black. Each embryo displayed a spherical shape, measuring approximately 280 μm in diameter, characterized by a smooth surface devoid of any depressions. The embryonic cell division was in the form of mixed oogenesis, comprised of complete division in the early stage, spiral oogenesis in the middle stage and surface division in the late stage. It is noteworthy that the blastopore appeared at the position where the transparent area and cell aggregation just appeared under the microscope, and the blastomere was a characteristic of the embryo entering the gastrulation stage. After entering the gastrulation stage, the cells aggregated towards the blastopore and formed two symmetrical cell clusters, which formed a V-shape with the void of the classic blastopore. When the transparent region occupied approximately 1/5 of the embryo’s volume, the embryo entered the nauplius stage, and the thoracic and abdominal armor, as well as the optic lobe and abdominal limb primordia, could be clearly distinguished. The appearance of the compound eye pigment band indicated the stage of compound eye pigment formation. At this time, the transparent area accounted for 1/4 of the embryo and a large number of ganglia appeared. The change of the compound eye pigment band from red to black was also one of the reasons for the blackening of the egg color of the crabs. The data obtained through this study have potential applications in the determination of embryonic development status and obtaining of high-quality seeds for S. paramamosain culture.

Dietary intake is an essential source of energy and nutrients, and plays an irreplaceable role in the breeding of S. paramamosain seedlings. In this study, live Artemia nauplii (LA), compound feeds (CF), frozen copepods (FC) and frozen adult Artemia (FA) were utilized as feed during the megalopa stage. To determine the impact that diet has on the metabolism of crablets that underwent metamorphosis from the megalopa stage, analyses of both metabolomics and fatty acid content were conducted. In the LC-MS-based metabolomics analysis, a total of 104, 205 and 83 significantly different metabolites (SDMs) were identified after being fed with FC, FA, and CF, respectively, as compared to the LA group. Furthermore, significant differences in KEGG compounds among the three comparisons exhibited similarity and were mainly associated with categories such as “Lipids”, “Hormones and transmitters”, and “Peptides”. The fatty acid content analysis indicated that the ΣMUFA was significantly higher in the LA and CF groups compared to the other two groups. In contrast, the highest level of ΣPUFA was found in the LA group. In addition, the CF group showed significantly higher expression levels of the fatty acid synthesis genes, FAS and ACC. Conversely, the expression level of the fatty acid decomposition-related gene CPT1 was the highest in the LA group. In comparison with the FA group, the expression level of FABP3 was significantly decreased in the LA and CF groups. In summary, there were significant differences observed in the metabolic profiles of crablets that metamorphosed from the megalopa under different diets. Our experimental results suggested that LA is more advantageous in the cultivation of the S. paramamosain megalopa compared to the other three diets. While it remains a diet that cannot be entirely substituted at present, LA has the potential to improve the culture performance of the S. paramamosain megalopa. The current study could provide valuable data into the development of artificial diets necessary for the future of the mud crab seedling breeding industry.

Introduction: Elongation of very long-chain fatty acids protein 6 (ELOVL6) played crucial roles in regulating energy expenditure and fatty acid metabolism. Many studies have performed to investigate the physiological roles and regulatory mechanisms of elovl6 in fish and animals, while few studies were reported in crustaceans. Methods: Here we reported on the molecular cloning, tissue distribution and expression profiles in response to dietary fatty acids, ambient salinity and starvation stress in Scylla paramamosain by using rapid amplification of cDNA ends (RACE) and quantitative real-time PCR. Results: Three elovl6 isoforms (named elovl6a, elovl6b and elovl6c) were isolated from S. paramamosain in the present study. The complete sequence of elovl6a was 1345 bp, the full-length sequence of elovl6b was 1419 bp, and the obtained elovl6c sequence was 1375 bp in full length. The elovl6a, elovl6b and elovl6c encoded 287, 329 and 301 amino acids respectively, and exhibited the typical structural features of ELOVL protein family members. Phylogenetic analysis showed that the ELOVL6a from S. paramamosain clustered most closely to ELOVL6 from Portunus trituberculatus and Eriocheir sinensis, while the ELOVL6b and ELOVL6c from S. paramamosain gathered alone into a single branch. Quantitative real-time PCR exhibited that the relatively abundant expression of elovl6b was observed in intestine and stomach, and the elovl6a and elovl6c were highly expressed in hepatopancreas. In addition, studies found that replacing fish oil with soybean oil could significantly increase the transcriptional levels of three elovl6 in hepatopancreas of S. paramamosain, and the expression of elovl6a and elovl6c in hepatopancreas were more sensitive to dietary fatty acids than the elovl6b. Compared with the normal sea water group (27?), the expression of sterol-regulatory element binding protein1c (srebp-1), elovl6a, elovl6b and elovl6c were upregulated in the low salinity groups, particularly in 7?. On the contrary, the starvation stress suppressed the expression of srebp-1, elovl6a, elovl6b and elovl6c. Discussion: These results may contribute to understand the functions of elovl6 in fatty acid synthesis and regulatory mechanisms in crustaceans. [ABSTRACT FROM AUTHOR]

Background: For more than a century, the Koch's postulates have been the golden rule for determining the causative agents in diseases. However, in cases of multiple pathogens-one disease, in which different pathogens can cause the same disease, the selection of microorganisms that regress infection is hard when Koch's postulates are applied. Microbiome approaches can obtain relatively complete information about disease-related microorganisms and can guide the selection of target microorganisms for regression infection. In the present study, whitish muscle syndrome (WMS) of Scylla paramamosain, which has typical symptoms with whitish muscle and blackened hemolymph was used as an example to establish a new research strategy that integrates microbiome approaches and Koch's postulates to determinate causative agents of multiple pathogens-one disease. Results: Microbiome results revealed that Aeromonas, Acinetobacter, Shewanella, Chryseomicrobium, Exiguobacterium, Vibrio and Flavobacterium, and Kurtzmaniella in hemolymph were bacterial and fungal indicators for WMS. A total of 23 bacteria and 14 fungi were isolated from hemolymph and muscle tissues, and among the bacteria, Shewanella chilikensis, S. xiamenensis, Vibrio alginolyticus, S. putrefaciens, V. fluvialis, and V. parahaemolyticus were present in hemolymph and/or muscle tissues in each WMS crab, and the last three species were also present in three Healthy crabs. The target bacteria and fungi were further screened to regression infections based on two criteria: whether they belonged to the indicator genera for WMS, whether they were isolated from both hemolymph and muscle tissues in most WMS crabs. Only S. chilikensis, S. putrefaciens, S. xiamenensis, V. alginolyticus, V. fluvialis, and V. parahaemolyticus met both two criteria. The six bacteria that met both two criteria and six fungi and another bacterium that unmatched any of two criteria were used to perform regression infection experiments based on Koch's postulates. S. chilikensis, S. putrefaciens, S. xiamenensis, V. alginolyticus, V. fluvialis, and V. parahaemolyticus met both two criteria, and the results indicate that they cause WMS in crabs independently. Conclusions: This study fully demonstrated that our research strategy that integrates the microbiome and Koch's postulates can maximize the ability to catch pathogens in one net for the situation of multiple pathogens-one disease. EgKJnBsvf5xgzELdpRDt_Q Video Abstract [ABSTRACT FROM AUTHOR]

Copyright of South China Fisheries Science is the property of South China Fisheries Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Mesanophrys sp. is reported to be highly pathogenic to marine crustaceans. This study presents the first report of Mesanophrys sp. infection in the mud crab (Scylla paramamosain). In this study, we first recorded the survival rates of an experimentally infected group and a control group; the cumulative survival rate in the infected group was significantly lower compared to the control group after 72 h (73.20% vs. 94.19%), while the highest mortality of S. paramamosain occurred within the first 24 h post-infection. Then, we investigated the dynamic distribution and tissue tropism of the Mesanophrys sp. in the infected S. paramamosain by a quantitative real-time polymerase chain reaction (qPCR). The result showed that a significant increase in the number of Mesanophrys sp. could be detected in all tested tissues (obtained from the eyestalks, gills, heart, nerves, muscles and hepatopancreas) at 3 h post-infection. The numbers of Mesanophrys sp. in the gill, eyestalk and nerve tissues were relatively higher than in the other tissues. The gill tissue showed the highest numbers from 6 to 48 h. Histopathological observation found a severe collapse in the filament structure, which indicated tissue-specific pathogen infection. Furthermore, the antioxidant enzyme activity of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) in three representative tissues (gill, muscle and hepatopancreas) were compared between the infected and control groups, and a significant increase in enzyme activity was observed in all three tested tissues in the infected group, indicating a relatively strong innate immune defense reaction that could have been induced by Mesanophrys sp. infection. These results will be helpful to Mesanophrys sp. pathogenicity-related research and the control of this pathogen in S. Paramamosain in the future. [ABSTRACT FROM AUTHOR]

Copyright of Jurnal Ilmu dan Teknologi Kelautan Tropis is the property of IPB University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the study, a new gene homologous to the known antimicrobial peptide Scygonadin was identified in mud crab Scylla paramamosain and named SCY3. The full-length sequences of cDNA and genomic DNA were determined. Similar to Scygonadin, SCY3 was dominantly expressed in the ejaculatory ducts of male crab and the spermatheca of post-mating females at mating. The mRNA expression was significantly up-regulated after stimulation by Vibrio alginolyticus, but not by Staphylococcus aureus. The recombinant protein rSCY3 had a killing effect on Micrococcus luteus and could improve the survival rate of mud crabs infected with V. alginolyticus. Further analysis showed that rSCY3 interacted with rSCY1 or rSCY2 using Surface Plasmon Resonance (SPR, a technology for detecting interactions between biomolecules using biosensor chips) and Mammalian Two-Hybrid (M2H, a way of detecting interactions between proteins in vivo). Moreover, the rSCY3 could significantly improve the sperm acrosome reaction (AR) of S. paramamosain and the results demonstrated that the binding of rSCY3, rSCY4, and rSCY5 to progesterone was a potential factor affecting the sperm AR by SCYs on. This study lays the foundation for further investigation on the molecular mechanism of SCYs involved in both immunity and physiological effects of S. paramamosain. [ABSTRACT FROM AUTHOR]

The mud crab, Scylla paramamosain, has abundant nutrients in the ovary, where numerous lipids accumulate during ovarian maturation. However, the mechanism behind the accumulation of lipids in the ovary of mud crab during ovarian maturation is largely unknown. This study conducted a comparative transcriptome analysis of the ovaries of mud crabs at various stages of ovarian maturation. A total of 63.69 Gb of clean data was obtained, with a Q30 of 93.34%, and 81,893 unigenes were identified, including 10,996 differentially expressed genes (DEGs). After KEGG enrichment of these DEGs, MAPK signaling pathway was significantly enriched during vitellogenesis. Moreover, the expression levels of genes involved in carbohydrate, amino acid, and lipid metabolism were found to be higher during vitellogenesis. The two genes (Sp-Eip75B and Sp-Eip78C) that are homologous to the vertebrate gene PPARγ in the PPAR signaling pathway, were identified. Additionally, genes in MAPK signaling pathway might regulate lipid metabolism through PPAR signaling pathway based on Protein-Protein Interaction (PPI) network. These findings suggest that MAPK signaling pathway plays a critical role in lipid metabolism in the ovary during vitellogenesis, which provides new insights into the mechanism of lipid accumulation during ovarian maturation in mud crabs. [ABSTRACT FROM AUTHOR]

Providing shelters is considered an effective method to prevent self-harm and improve the survival rate of Scylla paramamosain. In this study, four shelter groups—the shelters of which included fine sand, arched tiles, PVC pipes, and trapezoidal net cages—and one group without shelters were established to investigate the effects of shelters on S. paramamosain by calculating their feeding rate, molting rate, survival rate, and growth index. The results showed that the feeding rates of the fine sand and PVC pipe groups were greater than 12% and that the feeding rates of the arched tile and trapezoidal net cage groups were greater than 9%, while the feeding rate of the group without shelters was only 6.7%. The food conversion rates of both the fine sand and PVC pipe groups exceeded 21%. In contrast, the food conversion rate of the non-shelter group was the lowest at 14%. The molting rates of the fine sand and PVC pipe groups were the highest, reaching 29% in the later stages of the experiment, while the molting rate of the non-shelter group was only 19%. There was no significant difference in survival rates among the groups during the first 20 days of the experiment. However, on the 60th day, the survival rate of the fine sand group was 92%, while the non-shelter group had a survival rate of 79%. The experimental results showed that the incidence of cheliped injuries in the fine sand group was 16%, while it was 25% in the non-shelter group. During the daytime, the occupancy rate of burrows by the four shelter groups was 60–70%, while during the night, the occupancy rate of each shelter decreased to 40–50%, and there was no significant difference in occupancy rates among the shelter groups during the night. The weight and full carapace width of S. paramamosain in the fine sand and PVC pipe groups were significantly higher than those in the other groups (P< 0.05), and the weight gain rate and specific growth rate of the fine sand and PVC pipe groups were significantly higher than those of the other groups (P< 0.05). Research has shown that fine sand and PVC pipes, as shelters for S. paramamosain, can effectively prevent cannibalism, increase feeding rates and survival rates, and promote growth and molting. This study provides scientific guidance for the proper selection of shelters in the farming process of S. paramamosain.

Saline–alkali water represents a huge underdeveloped resource due to its harsh properties of high pH, high salinity, and complex ionic composition. In our previous research, the mud crab, Scylla paramamosain could adapt to the saline–alkali environment, which may bring dual benefits to high-quality aquaculture and the utilization of saline–alkali water. Yet, no systematic study related to S. paramamosain's ability to carbonate alkali, the key gene responsible for adaptation to the harsh environment, has been reported. In this study, we investigated the mud crab's response to a wide range of carbonate–alkali waters, verifying the specific gill tissue with the highest carbonic anhydrase (CA) expression. Afterward, we cloned the CA gene in S. paramamosain (Sp-CA) for the first time. The cDNA sequence is 1085 bp, with a 55-bp 5′-untranslated region (UTR) and 214-bp 3′-UTR. The open reading frame (ORF) of 816-bp nucleotides encodes a polypeptide of 271 amino acids (AAs). In silico analysis and phylogenetic analysis of crustacea's CAs were performed, elucidating the unique function and evolutionary relation of Sp-CA. We also conducted short-term and long-term stress experiments with mud crabs in a saline–alkali environment, with the relative mRNA expression and DNA methylation profile of Sp-CA under such stress having been clarified, bringing new insight into the understanding of mud crabs' adaptation and tolerance to a saline–alkali environment.

Variability in food availability leads to condition-dependent investments in reproduction. This study is aimed at understanding the metabolic response and regulatory mechanism of female Scylla paramamosain in response to starvation in a temporal- and tissue-specific manner. The mud crabs were starved for 7 (control), 14, 28, and 40 days for histological and biochemical analysis in the hepatopancreas, ovary, and serum, as well as for RNA sequencing on the hepatopancreas and ovary. We further highlighted candidate gene modules highly linked to physiological traits. Collectively, our observations suggested that starvation triggered endogenous ovarian maturation at the expense of hepatopancreas mass, with both metabolic adjustments to optimize energy and fatty acid supply from hepatopancreas to ovary in the early phase, followed by the activation of autophagy-related pathways in both organs over prolonged starvation. These specific adaptive responses might be considered efficient strategies to stimulate ovarian maturation of Scylla paramamosain under fasting stress, which improves the nutritional value of female mud crabs and other economically important crustaceans.

Anesthesia serves as an effective method to mitigate the stress response in aquatic animals during aquaculture and product transportation. In this study, we assessed the anesthetic efficacy of clove oil, tricaine methane-sulfonate (MS-222), ethanol, and magnesium chloride by anesthesia duration, recovery time, 24-hour survival rate, and the behavior of mud crabs (Scylla paramamosain). Additionally, the optimal anesthetic concentration for varying body weights of mud crabs was also investigated. The results revealed that clove oil emerged as the optimal anesthetic for mud crabs, with a 24-hour survival rate surpassing those observed in MS-222 and magnesium chloride treatments. Ethanol caused amputation and hyperactivity in mud crabs. Regression analyses between the optimal anesthetic concentration of clove oil and the weight categories of 0.03–27.50 g and 27.50–399.73 g for mud crabs yielded the following equations: y = 0.0036 x3 − 0.1629 x2 + 1.7314 x + 4.085 (R2 = 0.7115) and y = 0.0437 x + 2.9461 (R2 = 0.9549). Clove oil exhibited no significant impact on serum cortisol, glucose, lactate content, aspartate aminotransferase (AST), alanine aminotransferase (ALT) activities, or superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), and malondialdehyde (MDA) levels in mud crabs across different treatment groups. Anesthesia induced by clove oil in mud crabs resulted in an increase in inhibitory neurotransmitters such as glycine. However, the recovery from anesthesia was associated with elevated levels of the excitatory neurotransmitters L-aspartic acid and glutamate. In conclusion, clove oil proves to be a safe and optimal anesthetic agent for mud crabs, exerting no physiological stress on the species.

Three isonitrogenous diets (41% crude protein) with 4.87%, 10.75% and 16.10% lipid were designed to evaluate the effects of dietary lipid levels growth, antioxidant capacity, expression levels of genes related to lipid and glucose metabolism of juvenile Scylla paramamosain. Each diet was fed to four replicates of 32 crabs with initial weight 5.10 ± 0.05 g for 6 weeks. The results indicated that crabs fed diet with 10.75% lipid exhibited significantly higher percent weight gain (PWG) and specific growth rate (SGR) than those fed diet with 4.87% lipid (P

IntroductionThe intestinal microbiota acts as an additional “organ” that performs a variety of fu\nctions for the host’s health. However, the composition and role of the intestinal microbiota in Scylla paramamosain cultivated in inland low salinity saline-alkaline water are unknown.MethodsAccordingly, from the perspective of practical production, we explored the intestinal microbiota communities and the critical bacteria of S. paramamosain in normal salinity seawater (NS), coastal low salinity seawater (CS), acute low salinity seawater (AS) and inland low salinity saline-alkaline water (IS).ResultsResults showed that there were significant differences in the diversity composition of intestinal microbiota and the relative abundance of dominant taxa in each group of cultured crabs. Firmicutes, Proteobacteria, Bacteroidota and Campilobacterota were shown to be the major phyla shared by the four groups, with Bacteroidota having the highest relative abundance (27.10%) in the inland low salinity saline-alkaline water group (IS). Fusobacteriota had the highest proportion in IS group compared with other low salinity groups. A total of 284 indicator bacteria were identified, belonging to eight phyla, and their relative abundances were varied significantly (P < 0.05). Genus Carboxylicivirga, as the indicator bacterium of the IS group, may play a critical role in the adaptation of crab to saline-alkaline water environment. Moreover, salinity may exert considerable selective pressure on the entire microbial community.DiscussionThese findings revealed the features of the intestinal microbiome in S. paramamosain in multiple low salinity patterns, and provided candidate probiotics and basic information for crab farming in saline-alkaline water, which was conducive to the development and perfection of mud crab culturing technology in inland low salinity saline-alkaline water.

Biogenic amines (BAs) play an important role in the aggressive behavior of crustaceans. In mammals and birds, 5-HT and its receptor genes (5-HTRs) are characterized as essential regulators involved in neural signaling pathways during aggressive behavior. However, only one 5-HTR transcript has been reported in crabs. In this study, the full-length cDNA of the 5-HTR1 gene, named Sp5-HTR1, was first isolated from the muscle of the mud crab Scylla paramamosain using the reverse-transcription polymerase chain reaction (RT-PCR) and rapid-amplification of cDNA ends (RACE) methods. The transcript encoded a peptide of 587 amino acid residues with a molecular mass of 63.36 kDa. Western blot results indicate that the 5-HTR1 protein was expressed at the highest level in the thoracic ganglion. Furthermore, the results of quantitative real-time PCR show that the expression levels of Sp5-HTR1 in the ganglion at 0.5, 1, 2, and 4 h after 5-HT injection were significantly upregulated compared with the control group (p < 0.05). Meanwhile, the behavioral changes in 5-HT-injected crabs were analyzed with EthoVision. After 0.5 h of injection, the speed and movement distance of the crab, the duration of aggressive behavior, and the intensity of aggressiveness in the low-5-HT-concentration injection group were significantly higher than those in the saline-injection and control groups (p < 0.05). In this study, we found that the Sp5-HTR1 gene plays a role in the regulation of aggressive behavior by BAs, including 5-HT in the mud crab. The results provide reference data for the analysis of the genetic mechanism of aggressive behaviors in crabs. [ABSTRACT FROM AUTHOR]

Soft-shell crabs have attracted consumers' attention due to their unique taste and nutritional value. To evaluate the feasibility of harvest optimisation of soft-shell mud crabs, the proximate composition, mineral composition, and total carotenoid, amino acid, and fatty acid contents of edible parts of male and female soft-shell mud crabs at different moulting stages were determined and compared from a nutritional value perspective. The results showed that the sex and moulting stages could significantly affect the nutritional values of the edible portions of soft-shell crabs. The female or male soft-shell crabs in the postmoult Ⅰ stage had a much richer mineral element content than that in other moulting stages. The total carotenoid content in female soft-shell crabs was significantly higher than that in male crabs in all moulting stages, while male soft-shell crabs had better performance in amino acid nutrition than female soft-shell crabs. Moreover, it was found that soft-shell crabs in the postmoult Ⅱ stage had significantly higher contents of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), while significantly lower contents of saturated fatty acids (SFA) than those in other stages. The present study will provide a reference basis for the diversified cultivation of soft-shell crabs, and further promote the development of the mud crab industry. [ABSTRACT FROM AUTHOR]

Mud crab (Scylla paramamosain) fed five different diets with varying concentrations of guava leaf aqueous extract (0 mg·kg-1, 80 mg·kg-1, 160 mg·kg-1, 320 mg·kg-1, and 640 mg·kg-1) for 30 days. Mud crabs in the 320 mg·kg-1 guava-leaf extract groups outperformed the control group in terms of survival rates (SR), weight gain rates (WGR), and specific growth rates (SGR). When compared to the control group, mud crabs in the 320 mg·kg-1 guava-leaf extract groups had significantly higher levels of lipase (LPS), pepsin, lysozyme (LZM), superoxide dismutase (SOD), acid phosphatase (ACP), and glutathione (GSH) (P < 0.05). The amylase (AMS) activity was significantly decreased in all experimental groups (P < 0.05). Malondialdehyde (MDA) content in the hepatopancreas of mud crabs in the 160 mg·kg-1, 320 mg·kg-1, and 640 mg·kg-1 guava-leaf extract groups were significantly reduced compared to the control group (P < 0.05). Additionally, real-time PCR results illustrated that the expression levels of GPx3, CAT, and JNK were all considerably increased in the 80 mg·kg-1 guava-leaf extract groups compared to the control group (P < 0.05). In the 160 mg·kg-1, 320 mg·kg-1, and 320 mg·kg-1 guava-leaf extract groups, the expression levels of SOD genes were considerably greater than the control (P < 0.05), which was consistent with the level of SOD activity. GST and P53 gene expression levels were significantly up-regulated in the 80 mg·kg-1, 160 mg·kg-1, 320 mg·kg-1, and 640 mg·kg-1 guava-leaf extract groups compared to the control group (P < 0.05). Overall, the addition of 160 mg·kg-1-320 mg·kg-1 guava-leaf extract to the feed of Scylla paramamosain promoted growth, enhanced the activities of digestive and antioxidant enzymes, and strengthened immunity. [ABSTRACT FROM AUTHOR]

The function and molecular characterization of the previously reported crab (Scylla paramamosain) vitellogenesis inhibiting hormone SpVIH is still unclear. In this experiment, SpVIH's bioinformatic and functional characterizations were analyzed. Sequence analysis showed SpVIH was clustered with several type II MIH/GIHs of the Brachyura. The expression of SpVIH in the eyestalk was low in the early ovarian developmental stage I and increased with the advancement of ovary maturation. Interestingly, the SpVIH transcript was still at a high level in the ovary of females at the middle to late maturation stage. SpVIH's function was studied according to the expression of vitellogenin (Vg) and vitellogenin receptor (VgR) in the ovary and hepatopancreas after incubation with SpVIH-dsRNA and recombinant SpVIH protein (rSpVIH). In vitro assay results indicated that rSpVIH has a significant stimulative effect on the expression of Vg in the hepatopancreas in the middle stage of vitellogenesis and in the ovary of each vitellogenesis stage. However, SpVIH-dsRNA has no significant effect on the expression of Vg when SpVIH-dsRNA is introduced to the ovary and hepatopancreas at the early, middle, and late stages of vitellogenesis. Furthermore, the co-incubation experiment result indicated that the eyestalk consists of factor(s) that can significantly up-regulate the expression of Vg in the ovary, with a further combination of dsVIH and eyestalk under incubation, the significant increase of Vg-mRNA expression levels were also found in the ovary of four ovarian development stages of S. paramamosain. Contrary to the previous reports, SpVIH does not possess a vitellogenesis-inhibiting function but can promote vitellogenesis in the ovary and hepatopancreas. [ABSTRACT FROM AUTHOR]

Hypoxia is a major environmental stressor that can damage the oxidation metabolism of crustaceans. Glutaredoxin (Grx) is a key member of the thioredoxin superfamily and plays an important role in the host's defense against oxidative stress. At present, the role of Grx in response to hypoxia in crustaceans remains unclear. In this study, the full-length cDNA of Grx3 (SpGrx3) was obtained from the mud crab Scylla paramamosain, which contains a 129-bp 5′ untranslated region, a 981-bp open reading frame, and a 1,183-bp 3′ untranslated region. The putative SpGrx3 protein contains an N-terminal thioredoxin domain and two C-terminal Grx domains. SpGrx3 was expressed in all tissues examined, with the highest expression in the anterior gills. After hypoxia, SpGrx3 expression was significantly up-regulated in the anterior gills of mud crabs. The expression of Grx2 and glutathione S-transferases was decreased, while the expression of glutathione peroxidases was increased following hypoxia when SpGrx3 was silenced in vivo. In addition, the total antioxidant capacity of SpGrx3-interfered mud crabs was significantly decreased, and the malondialdehyde content was significantly increased during hypoxia. The subcellular localization data indicated that SpGrx3 was predominantly localized in the nucleus when expressed in Drosophila Schneider 2 (S2) cells. Moreover, overexpression of SpGrx3 reduced the content of reactive oxygen species in S2 cells during hypoxia. To further investigate the transactivation mechanism of SpGrx3 during hypoxia, the promoter region of the SpGrx3 was obtained by Genome Walking and three hypoxia response elements (HREs) were predicted. Dual-luciferase reporter assay results demonstrated that SpGrx3 was likely involved in the hypoxia-inducible factor-1 (HIF-1) pathway during hypoxia, which could be mediated through HREs. The results indicated that SpGrx3 is involved in regulating the antioxidant system of mud crabs and plays a critical role in the response to hypoxia. [ABSTRACT FROM AUTHOR]

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The fibroblast growth factor receptor (FGFR) belongs to the tyrosine kinase family consisting of four members (FGFR1-4). This study involved identification and characterization of FGFR1 and FGFR3 from mud crab Scylla paramamosain for the first time. The obtained cDNAs of SpFGFR1 and SpFGFR3 were 2,380 bp and 2,982 bp in length with a 1,503 bp and 2,310 bp open reading frame, respectively. The predicted Sp FGFR1 protein included three immunoglobulin domains and a transmembrane region, while SpFGFR3 protein possessed a typical TyrKc (Tyrosine kinase, catalytic) domain. Real-time PCR analysis showed that SpFGFR1 and SpFGFR3 were highly expressed in the hepatopancreas. Furthermore, the expression levels of SpFGFR1 and SpFGFR3 in the hepatopancreas were enhanced following challenges with Vibro alginolyticus, Staphylococcus aureus , Poly (I:C) and White spot syndrome virus , which shows the involvement of SpFGFR1 and SpFGFR3 in innate immune response to infections from bacteria and virus. There was significant suppression of six antimicrobial peptide genes (SpALF1-5 and SpCrustin) and three NF-κB members (SpDorsal, SpIKK and SpRelish) when SpFGFR1 and SpFGFR3 was interfered in vivo. Also, treatment of the hemocytes with specific inhibitor of Sp FGFR for 24 h consistently down-regulated SpDorsal, SpRelish and AMPs. These results suggested that SpFGFR1 and SpFGFR3 played important roles in regulating the Toll signaling pathway and immune deficiency (IMD) pathway through NF-κB signaling pathway. These findings may provide new insights into the role of FGFR s in the innate immune function of crustaceans. • The SpFGFR1 , SpFGFR3 genes were firstly identified and characterized. • FGFR existed in crab and responded to bacterial and viral infection. • FGFR regulated expressions of antimicrobial peptides genes in S. paramamosain. [ABSTRACT FROM AUTHOR]